Ignition Voltage Question

I have a 73 850 with the Boyer MKIII electronic ignition. The ignition has worked well in the past. I had an ignition wire rub its insulation off due to vibration. I have now repaired the wire.

I have removed both spark plugs to mak kicking the bike easier. I have hooked up a voltage meter to the spare negative terminal on the coil.

What type of voltage reading should I see as I kick th bike over a few times?

Thanks,

Bob

Hi Bob,
I assume that you are running the standard + positive ground series connected two coil system. So I imagine at the first negative coil terminal you should see 12 volts (battery voltage), and at the second negative terminal 6 volts (1/2 battery voltage). As to what changes you'll see as you kick it over I haven't a clue due to the fact that the coils will be charging, reaching saturation, and discharging very rapidly. I don't think you will be able to attain any meanful voltage reading by doing what you have described.

GB

Bob

If you put a test lead on the first negative coil terminal fed by the box (assuming a normal Boyer setup) and kick it through you should see voltages flickering from perhaps 11V DC down to zero and back, with all kinds of readings in between. The plugs or plug wires need to be grounded.

If there's steady voltage or no voltage when you kick through with the ignition on, the box is not switching. Either the box is dead or something else is amiss, like incorrect wiring, a dead coil or rotor or stator problems. Without fluctuating voltage at the lead coil the system simply won't fire. The box needs make/break input from the stator and rotor to switch the coils on and off.

Good luck


Tim Kraakevik
kraakevik@voyager.net
Three '72-'74 Nortons
2

Just one item that needs to be clear - 12 volts at the batt under no load in a 12V system indicates the battery has less than 25% of its charge. When I had a Boyer on the bike, I found that a no-load batt voltage below around 12.3 (50% charged) was problematic. If your battery is fully charged, it should show around 12.6V with no load.

Thanks for the input. I was getting about 5 volts with the plugs not grounded. I will ground the plugs and try again tonight.

Bob

Tim - I left my battery on a trickle charger for a couple of days. I took at voltage reading and I had 13.4 volts at the battery. I grounded the plugs. I kicked the bike through a few times and only measured voltage up to 5 volts.

I think my grounded ignition wire did some damage to the Boyer MKIII system.

From what I have read via the search engine, Tri-Spark seems to be one of the better new systems out there.

I ordered one and will give it a try. Most popele said it really aided cold starting.

Bob

Bob

You may still have a bad coil or connection. If the box is switching there will be fluctuating voltage with two good coils. If you have fluctuating readings the box, stator and rotor are probably good. You may want to hang on to the Boyer setup as a backup for your Tri-Spark, as I have--or to use on another bike.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos

The tri spark is superb; I heartily recommend it as "THE" elec ign for a Commando. It's been on my bike for a couple of months now and is superior to the analog boyer for starting, mid range power, idle smoothness, and it needs much less power to operate properly. The electronics consist of one little unit that fits entirely in the points cavity - no other "boxes" involved.